The invention relates to a method for the melting and treatment of metals and metal alloys, especially steels, in the form of solid charge material in metallurgical vessels with the input of electrical energy.
The charge material in this case is especially scrap in pieces. Formerly the procedure has been to melt down the solid charge material in an electric arc furnace, decarburize it, dephosphorize it and roughly alloy it. After the desired temperature is reached the melt, which is quite largely slag-free, is tapped into a ladle. Then a reactive flux mixture, which can consist, for example, of a mixture of CaO and CaF.sub.2, is fed to the melt in the ladle. Then, in the further treatment of the melt, the ladle is heated in an electric ladle furnace to compensate temperature losses. If it should be necessary, the melt is alloyed during this heating phase to achieve the desired chemical composition.
Depending on the specifications given the melt is degassed in a degassing apparatus. In the production of low-carbon alloys of high chromium content the melt is blasted with oxygen in the degassing apparatus and decarburized under reduced pressure (the so-called VOD process). In the VOD process, the heating in the ladle furnace is usually omitted, since sufficient heat is formed during decarburization by the exothermic carbon monoxide reaction. After this treatment is completed the melt is cast either by the strand-casting or by the teeming method.
This long-common practice, however, has the following disadvantages: First of all, a special melting apparatus, such as an electric arc furnace is required. This involves high first costs, additional space for the furnace, an extensive stock of replacement parts and additional consumption of refractory material for preparation and lining of the oven. Furthermore, personnel costs for the furnace crew are considerable. While the furnace is being prepared or serviced there is a loss of production. When the furnace is tapped into the ladle additional heat losses occur, which have to be compensated in the ladle furnace.
The proposal has never before been put forward that the entire melting process, i.e., the use of solid charge material, be performed in a single crucible, which is referred to also as a transfer ladle. Transfer ladles have as a rule been filled with metal that is already molten, and then many different treatments are performed in the ladle.
DE-OS37 22 167 has already disclosed the melting of solid material in a ladle, which consists of a so-called consumable electrode. For this purpose it is also necessary first to charge the ladle with molten metal, and the melting of the consumable electrode is done only for the purpose of feeding certain substances to the metal, such as additional alloying elements. The amount of metal fed via the consumable electrode amounts to only a fraction of the total amount of metal.